1. Field of Invention
The invention relates to a filter and a manufacturing method thereof. More particularly, the invention relates to a common mode filter and a manufacturing method thereof.
2. Related Art
Recently, applications of power electronic circuits are widely spread and this kind of circuits usually operate in a high-frequency switching state, so electro magnetic interference (EMI) is easily occurred. The high-frequency noises may be conducted through the electromagnetic radiation or power lines to interfere with normal works of other electronic apparatuses. The conductive EMI can be a differential mode (DM) noise or a common mode (CM) noise according to different noise current transferring paths.
In order to eliminate the EMI effectively, a filter for eliminating a kind of the noises is usually equipped in the electronic apparatus. For example, when the common mode noises are to be eliminated, a common mode filter for eliminating the common mode noises is equipped in the electronic apparatus.
The common mode filter suppresses the common mode noises and prevents the signals transmitted in the circuit from being distorted. The conventional common mode filter has a magnetic layer serving as a substrate having a thickness of about several hundreds of microns (about 300 microns).
However, the magnetic layer cannot be easily formed and has the thickness of several hundreds of microns (about 300 microns). Therefore, when the conventional common mode filter operates at the high-frequency band, a lot of transmission loss may occur.